Vaibhav Upadhyay and Krishna Mallela in The Conversation:
A major reason why new vaccines are important – and why the world is still dealing with COVID-19 – is the continued emergence of new variants. Most of the differences between variants are changes in the spike protein, which is on the surface of the virus and helps it enter and infect cells.
Some of these small changes in the spike protein have allowed the coronavirus to infect human cells more efficiently. These changes have also made it so that previous vaccinations or infections with COVID-19 provide less protection against the new variants. Updated or new vaccines could be better at detecting these different spike proteins and better at protecting against new variants.
So far, 38 vaccines have been approved around the world, and the U.S. has approved three of those. There are currently 195 vaccine candidates at different stages of development worldwide, out of which 41 are in clinical trials in U.S. Vaccines against SARS-CoV-2 can be broadly divided into four classes: whole virus, viral vector, protein-based and nucleic acid-based vaccines.
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